Shuttle drive mechanism for a sewing machine



May 8, 1956 C. H. SPARKLIN SHUTTLE DRIVE MECHANISM FOR A SEWING MACHINE Filed Feb. 25, 1950 2 Sheets-Sheet 1 May 8, 1956 2,744,412

C. H. SPARKLIN SHUTTLE DRIVE MECHANISM FOR A SEWING MACHINE 2 Sheets-Sheet 2 Filed Feb. 25, 1950 United States Patent SHUTTLE DRIVE MECHANISM FOR A SEWING MACHINE Charles, H. Sparklin, Chicago, Ill assignor to Birtman Electric Company, a corporation of Illinois Application February 25, 1950, Serial No. 146,226 3 Claims. (Cl. 74-66) This invention relates to a sewing machine, and particularly to apparatus for driving a rotary shuttle in 'a sewing machine.

The ordinary sewing machine includes a main drive shaft ordinarily located in the upper portion of the machine and a rotary shuttle drive shaft in the base of the machine, together with a pitman connecting the two shafts for imparting rotary movement to the shuttle driveshaft. The connection to the shuttle drive shaft is ordinarilysuch that. the rotary shuttle which usually employs a hook to grasp the thread and form a loop will be driven at different rates of speed at different parts ofits pat'hj- In the usual sewing machine, the main drive shaft is bent to form a crank and the pitman is ordinarily made of'castmetal split to surround the bearing'portion of the crank-and locked in place bya screw or the like. This prior-arrangement has many disadvantages in that the bending'of' the drive shaft to form a crank is an expensive operation; and it is difficult to obtain the necessary alignmerit of the parts. The cast metal pitman 'is also expensive toproduce and is heavy so that vibration and noise are excessive.

In the present invention I avoid bending the drive shaft to form; a crank by employing a straight shaft with an eccentric block thereon. This eccentric is of light weight and is preferably made of nylon, powdered metal and the like. The pitman, instead ofbeing a heavy casting is preferably a sheet metal stamping of very light weight. By employing a straight shaft, the cost of the drive mechanism is considerably reduced and it is not difficult to obtain proper alignment of the parts. The eccentric and the pitman being of light weight materials are not only relatively inexpensive but also reduce vibration and noise.- I

In the preferred construction, the eccentric is constructed-sothat itwillhave asmall throw thatis not substantially greater than the diameter of the dri-veshaft. In-"the former constructions the throw of the drive shaft crankwas-considerably greater than the diameter of'the drive shaft andthis resulted in increased vibration and noises This throw may be describedas the radius of the circle-described-by the center of the eccentricduring its rotation and, as is pointed out above, in the present invention this throw is not substantially greater than the diameter of the drive shaft.

in the preferred construction, theeccentric is provided with a hollow interior bounded by acircular fiange=which is rotatablyenga-ged by the pitman and acts as a bearing surface. This hollow interior. reduces the weight of the eccentric and also provides for lubrication as an oil wick is preferably'positioned in this interior. This hollow interior is preferably bounded by the, circular flange and a closed-end. on theeccentric opposite this flange. The oil wick is located within this interior and a cover plate is provided closing the opening defined by the flange. With this arrangement adequate lubrication is provided between the eccentric and the pitman so that frequent oiling of the parts is not required. This cover plate preferably ice extends beyond the eccentric on the small side thereof to.

provide a counterweight.

The pitman, which is preferably of sheet metal, need only be heavy enough to furnish the required strength. This pitman is provided with a substantially circular flange engaging the eccentric flange to provide bearing surfaces; thus, even though the eccentric and pitman are made of light materials, adequate bearing surfaces are provided.

As is normally done in sewing machines, particularly of the household type, the pitman is arranged to slide on a fulcrum bearing member so that a combined rocking and sliding motion will be applied to the pitman. In my preferred construction, the pitman which is preferably a sheet metal stamping is provided with substantially parallel side flanges which engage the fulcrum bearing member and form bearing surfaces thereagainst. These side flanges serve to strengthen the light weight pitman and also give bearing surfaces of the required width to withstand wear. In the preferred construction, the pitman bearing surfaces at the eccentric, the fulcrum bearing member and the shuttle shaft connection lie in substantially a single plane so that bending forces on the pitman will be minimized. This also permits the use of an extremely light weight pitrnan such as a sheet metal stamping.

The invention will be described as related to the embodiment shown in. the accompanying drawings, Of the drawings: Fig. l is a side elevation partially in section of a sewing machine embodying the invention; Fig. 2 is a section taken substantially along line 22 of Fig. 1; Fig. 3 is a section showing the pitman and associated parts in elevation, but from the side opposite thatshown in Fig. 2; Fig. 4 is an enlarged section taken substantially along line 4-4 of Fig. 2; and Fig. 5 is an enlarged section taken substantially along line 55 of Fig. 2.

Thesewing machine shown in the accompanying drawings includes a base 10, standard 11, overhanging ,arm 12 and head 13. There is also provided the usual thread control arm 14, thread tensioner l5, needle bar .16 and spool holder 17. Located in the base 10 of the machine is a rotatable shuttle drive shaft 18 and shaft 19 for operating the feed dogs which are positioned adjacent the needle 20 in the base 10 of the machine.

Located within the top of the standard 11 and the overhanging arm 12 is a rotatable main drive or power shaft 21. Mounted on the end of this shaft opposite the head 13 is a fly wheel 22 driven by a motor 23 positioned within the standard ll. The motor and fly wheel driveshown in the drawings is described and claimed in the Buford W. Hulfish copending application Serial No. 155,293, filed April 11, 1950.

The drive shaft 21 which, as shown, isstraight, operates the usual mechanism 44 for operating the feed dog activating shaft 19.

Mounted on the main drive shaft 21 is a hollow eccentric 24 having a substantially circular eccentric flange 24a of appreciable width. The hollow interiorof the eccentric 24, which is defined by the eccentric flange 24a and a closed end 24b, is preferably provided with an oil wick 25 saturated with oil. The end of the eccentric opposite the closed end 24b is provided with a washer 26 andv a cover plate 27 held thereagainst by screws 28. This cover plate 27, as shown in Fig. 1, extends beyond the eccentric on the light side thereof and has mounted thereon a counterweight 2h for the eccentric. As can be seen, the eccentric 24 can be made of light weight material so as to reduce vibration and noise. The counterweight 29 also serves to reduce vibration. The eccentric 24 is preferably made of nylon or of compressed powdered metal.

As shown in Fig. 1, the closed end 24b of the eccentric extends beyond the outer surface of the eccentric flange 24a, with the washer 26 being substantially coextensive therewith. The surface of the flange 24:: be

tween the extended end 24b and the washer 26 forms a bearing surface for the pitman 30.

The pitman 30 is preferably made of a sheet metal stamping and is provided at the upper end with a substantially circular flange 30a closely embracing the outer surface of the eccentric flange 24a. As can be seen in Fig. 1, this pitman flange 30a extends between the inner edge of the extended portion of the closed end 2411 of the eccentric and the inner edge of the washer 26. With this arrangement the inner surface of the pitman flange 30a and the outer surface of the eccentric flange 24a form bearing surfaces which are lubricated by the oil in the oil wick 25.

The pitman 30 is provided with substantially parallel side flanges 30b along the central portion of the pitman. These side flanges serve to strengthen the pitman and also serve as bearings against which a fulcrum bearing member 31 slides. As shown most clearly in Fig. 4, this fulcrum bearing member extends between the flanges 30b and is mounted on a bearing collar 32, with the member 31 and collar 32 being held against the frame of the machine that forms a part of the standard 11 by a screw 33. The pitman is provided with a cut-out portion 30c through which the screw 33 extends and which provides space for movement of the pitman relative to the hearing member 31. This bearing member results in a combined sliding and rocking motion in the pitman as the drive shaft 21 and the eccentric 24 are rotated. The fulcrum bearing member 31 not only provides a bearing surface on which the pitman operates, but also serves to confine the movement of the pitman to a vertical plane. Thus, as shown in Fig. 4, the bearing collar 32 rests against a flat surface 11a on the inside of the standard 11 while the member 31 is provided with outwardly extending shoulders 31a bearing against the outer edges of the pitman side flanges 36b to hold the pitman again: this surface 11a. The head of the screw 3.: is spaced from the fulcrum bearing member 31 by a washer 34.

The end of the shuttle drive shaft 18 beneath the eccentric 24 has mounted thereon a crank 35 provided with substantially parallel side flanges 35H. Held between these flanges is a substantially circular bearing member 36 which is attached to the lower end of the pitman 30. The crank 35, side flanges 35a and bearing member 36 are substantially the same as similar members employed in prior sewing machines and are used to rotate the shuttle drive shaft 18 when the main drive shaft 21 is rotated.

As can be readily understood, the pitman 3b may be made of a light weight metal stamping. The weight of the stamping may be further reduced by providing cutout portions 3M and 33a at the top and bottom portions of the pitman.

As can be seen in Fig. l, the bearing surfaces at the eccentric 24, the fulcrum bearing member 31 and the shuttle drive member 36 lie approximately in a single plane. This arrangement minimizes the bending forces on the pitman so that the weight of the pitman may be reduced to a minimum.

By employing a straight drive shaft 21 and an eccentric 24 attached thereto, the throw or the radius of the circle described by the center of the eccentric may be kept to a minimum which is preferably not greater than the diameter of the drive shaft 21. This small throw reduces vibration and noise. As can be seen from the drawings, the entire assembly of pitman and associated parts including the eccentric 24 is of extremely light weight and relatively inexpensive to make. Tests of the assembly described and claimed show that the operation is extremely silent clue to the absence of heavy parts and high vibration.

Having described my invention as related to the embodiment set out herein, it is my intention that the invention be not limited by any of the details of description unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. In a sewing machine including a shuttle drive shaft, a power shaft, an eccentric fixed thereto including a flat plate having an outwardly extending substantially circular eccentric flange providing a bearing surface and a pitman having one end rotatably engaging said flange bearing surface and the other end engaging said shuttle drive shaft for rotation thereof, said eccentric being provided with a hollow interior bounded by said circular flange and a closed end opposite said flange, an oil wick within said interior, and a cover plate closing the opening defined by said flange, the cover plate extending beyond said eccentric to provide a counterweight for the eccentric.

2. A light weight eccentric for a sewing machine power shaft for connection through a pitman to a shuttle drive shaft for rotation thereof on rotation of the power shaft, the eccentric comprising a base attachable to the power shaft, a circular flange extending from this base and serving as a bearing for the pitman, and a closure plate extending across the open end of the circular flange to provide a sealed chamber within the eccentric, the closure plate extending beyond the circular flange on the light side of the eccentric and being provided with a weighted portion serving as a counterweight for the eccentric.

3. A light weight eccentric for a sewing machine power shaft for connection through a pitman to a shuttle drive shaft for rotation thereof on rotation of the power shaft, the eccentric comprising: a base having an opening therethrough for attachment to the power shaft; a circular flange extending from this base eccentrically located with respect to said opening and power shaft, the inner surfaces of the flange and of the base defining a hollow portion; and a closure plate extending across the open end of the circular flange, the closure plate extending beyond the circular flange on the light side of the eccentric and being provided with a weighted portion serving as a counterweight for the eccentric.

References Cited in the file of this patent UNITED STATES PATENTS 241,553 Leslie May 17, 1881 251,195 Davis Dec. 20, 1881 276,885 Roy May 1, 1883 284,071 Sargent Aug. 28, 1883 447,253 Mack Feb. 24, 1891 529,872 Morse Nov. 27, 1894 1,176,300 Layman Mar. 21, 1916 1,183,774 Schmitz May 16, 1916 1,196,524 Cluett Aug. 29, 1916 1,308,992 Pribil July 8, 1919 1,383,634 Johnson July 5, 1921 1,477,521 Richards Dec. 11, 1923 1,575,239 Walker Mar. 2, 1926 2,246,086 Austin June 17, 1941 2,369,535 Cofley Feb. 13, 1945 2,499,435 Fransen et al Mar. 7, 1950 FOREIGN PATENTS 400,165 France May 22, 1909 OTHER REFERENCES Product Engineering, pp. 103-107, December 1946. 

